Winslow Till Member

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Lithostratigraphy: Glasford Formation >>Winslow Till Member
Chronostratigraphy: Cenozoic Erathem >>Quaternary System >>Pleistocene Series

Primary source

Willman, H. B., and John C. Frye, 1970, Pleistocene Stratigraphy of Illinois: Illinois State Geological Survey Bulletin 94, 204 p.

Contributing author(s)

H. B. Willman and John C. Frye


Original description

The Winslow Till Member of the Glasford Formation was informally named the Winslow till (Frye et al., 1969, p. 25). It is herein formally named a member (Willman and Frye 1970).


The Winslow Till Member was named for Winslow, Stephenson County.

Other names


Type section

Type location

The type section is in roadcuts west of Winslow, SW SE SW Sec. 21, T. 29 N., R. 6 E., where 12 feet of dark gray clayey till, the upper 3 feet of which is leached, is exposed.

Type author(s)

Type status

Reference section

Reference location

Reference author(s)

Reference status

Stratigraphic relationships

Its stratigraphic relations are not adequately known, but its placement within the Glasford Formation is made on the basis of the Sangamon Soil that occurs above it. It may be still another lithologic variant of the Ogle, or it may be a stratigraphic equivalent of the Sterling Member, but, in either case, it has a distinctly different composition and should be treated as a distinct member. The Winslow Till is commonly bounded at the base by bedrock or by a residual soil developed in bedrock.

Extent and thickness

The geographic extent of the Winslow Till Member is shown in figure 6. It is generally less than 20 feet thick.


The till of the Winslow Member is distinguished from the till of the Ogle Member that partly surrounds it by its much higher clay content and gray color. Its typical composition is given in table 2.




Well log characteristics


Age and correlation

Its age is not firmly established, but it is judged to be in either the Monican or Jubileean Substages of the Illinoian Stage.

Environments of deposition

Economic importance



FRYE, J. C., H. D. GLASS, J. P. KEMPTON, and H. B. WILLMAN, 1969, Glacial tills of northwestern Illinois: Illinois State Geological Survey Circular 437, 47 p.

ISGS Codes

Stratigraphic Code Geo Unit Designation